This error says that Fixture.get('fixt1') is returning a null value, which means a fixture with id ‘fixt1’ doesn’t actually exist in the database. The get method returns the type object with the id you pass.

You may be able to confirm this with a c3Grid(Fixture.fetch()) which will display in static console all instances of Fixture in the system.

Have you actually upserted or merged the records yet to persist them in the database?

This will provision a package (without data), but this is not the package referred to in the instructions.
For the C3 Fundamentals course, the name of the package you should be provisioning is lightbulbExercise. For the rest of the course, make sure to change this field to say lightbulbExercise when provisioning the lightbulbExercise package. Please try provisioning again, but changing the field name.

We’re working on a fix to rename the tenant in this environment to avoid this confusion in the future.